Electro-hydraulic servo valves



July 18, 1967 J; 0. BUCHANAN 3,331,383

ELECTRO-HYDRAULI C SERVO VALVES Filed April 29, 1966 Sheets-Slugs; l

INVENTOR I W W July 18, 1967 J D. BUCHANAN ELECTRO-HYDRAULIC SERVOVALVES 5 Sheets-Shea 2 Filed April 29, 1966 VATW/KE/ July 18, 1967 J. D.BUCHANAN ELECTED-HYDRAULIC SERVO VALVES 3 Sheets-Sheet 5 Filed April 29,1966 INVENTOR.

United States Patent 3,331,383 ELECTRQ-HYDRAULIC SERVO VALVES J. D.Buchanan, 1100 Estelle Laue, Newport Beach, Calif. 92660 Filed Apr. 29,1966, Ser. No. 546,355 6 Claims. (Cl. 137-83) ABSTRACT OF THE DISCLOSUREElectro-hydraulic servo valve combining a polarized torque motor,controlling a jet pipe pilot valve, a rotary mounted jet receiver, afeedback lever between a power valve and the jet receiver to cause saidpower valve and said jet receiver to follow the pilot valve in responseto an electrical signal to the torque motor.

This invention relates to electro-hydraulic servo valves, and moreparticularly to dry coil servo valves, as shown in my US. Patent No.3,221,760.

In my US. Patent No. 3,221,760 and US. Patent No. 3,228,423, which use atube in bending as the pivot between the armature and flapper, it isfound that it is almost impossible to balance this design againstvibrational forces which unbalance the valve.

An object of the present invention is to avoid this problem. This isaccomplished by using a tube in torsion as the center of the masses.

A further object of the present invention is to eliminate a mechanicalconnection, more particularly a spring feedback, as shown in US PatentsNos. 2,947,268 and 2,884,- 9067, and the centering springs of the secondstage valve spool of US. Patent No. 2,767,689. This improvement of thepresent invention makes for a more reliable valve having moresensitivity, and hence, a higher response for a given electrical inputsignal.

As the operating environment of servo systems increases in temperature,the elimination of as many springs as possible in the system becomesparticularly important, if not an absolute necessity.

My former patent employs a flapper to control opposed pressure jets;whereas, the present invention employs an ejector jet positioned inoperative association with two receptor jets. A fluid under pressure isfed to the ejector jet and means are provided to move the ejector jet inresponse to an electrical signal to cause more or less of the fluidemitting from the ejector jet to enter one or the other of the receptorjets. The diiferential pressure generated across the valve spool and thedirection of this differential pressure will depend on the relativeproportion of the flow of fluid from the ejector jet which enters thereceptor jets.

A feature of the invention is the provision of a torque tube at oppositesides of the armature-ejector jet control element, these tubes beingarranged on a pivot axis extending transversely of the longitudinal axisof the control element. One of the tubes acts as a dry coil element, theother tube acting as a conduit to supply high pressure liquid to theejector jet.

A further feature of the invention is an improved feedback devicewherein the receptor jets are arranged at one end of a pivoted lever,the other end thereof being actuated by the valve spool. This provides afollow-up linkage to cause the receptor jets to follow the ejector jet,whereby the spool will assume at all times a position such that thepressures in its opposed control chambers are equal. When the electricalinput signal is removed, the torque action of the torque tubes serves toreturn the ejector jet, as well as the receptor jets, and the valvespool to null position.

A further object of the invention is to obtain a large gain in the ratioof hydraulic output flow from the power spool to the hydraulic input tothe jet and thus obtain a high efficiency. This is accomplished byarranging the receptor jets on a pivotal member at a certain radius andoperating the member :by a mechanical feedback arm of greater radius.

For further details of the invention, reference may be made to thedrawings wherein:

FIG. 1 is a perspective view of an electro-hydraulic servo valveaccording to the present invention.

FIG. 2 is an enlarged sectional view on the vertical plane indicated bythe lines 22 in FIG. 1.

FIG. 3 is a bottom view indicated by line 3-3 in FIG. 2.

FIG. 4 is a sectional view on line 44 of FIG. 2.

FIG. 5 is a top view as indicated by the line 55 in FIG. 4.

FIGS. 6 and 7 are schematic diagrams showing the parts in differentpositions for different electrical inputs.

FIG. 8 is a partial view showing the fluid path 29 in the jet spool 34from receptor jet 5 to the annular passage or channel 46, the similarpath 28 and channel 37 for the other receptor jet 4 being shown in FIG.4.

Referring in detail to the drawings, the electro-hydraulic valve 1comprises, in general, a torque motor, or polarized relay 2 whichoperates an ejector jet 3 ifi association with receptor jets 4 and 5which admit pressure to the opposite ends 6 and 7 of the power spool, orvalve spool 8, see FIG. 2. The power spool 8 has a mechanical feedbackdevice 9 for the receptor jets 4 and 5.

The torque motor 2 has permanent magnets 10 and 11, as well known, forthe armature 12 which has a pivotal support generally indicated at 13and described in detail later. The pivotal support 13 includes a torquetube 14 and a torque tube 15 on the pivot axis at opposite sides of theejector jet 3. The lower end of armature 12 has a lateral extension 16which is fixed to one side of the body of jet 3, as indicated at 17.Surrounding the extension 16, and coaxial with it, is the torque tube 14which is secured on a base 18 of the extension 16, at one end, the otherend of torque tube 14, as indicated at 19, being secured in a bore 20 ofthe cap, or first stage body 21. Cap 21 is secured on the top of thebase, or second stage body, 22 of the casing by means of bolts like 23and 24, see FIG. 2. The torque motor has a cover 61.

The interior of torque tube 14 opens into a chamber 25 in the cap 21,this chamber mating with a similar chamber 26 in the base 22. Theejector jet 3 and the receptor jets 4 and 5 open into the chambers 25and 26 which act as a return chamber to contain the fluid from thesejets.

The lateral extension 16 offsets armature 12 from ejector jet 3 armature12 and jet 3 extending in opposite directions from extension 16. Rotarymember 34 is parallel to extension 16 with feedback arm 53 offset fromreceptor jet 4, whereby feedback arm 53 swings in a plane passingthrough the center of coil 27, and the center of the cylinder for thepower spool is centered with the axis of the coil 27.

The torque tube 14 thus serves the double purpose of sealing off thefluid pressure in chamber 25 and 26 from the winding 27 of the torquemotor 2 as well as providing spring tension which cooperates with thetorque tube 15 to urge the ejector jet 3 to null position. The torquetube 15 assists the torque tube 14, as described, in providing a pivotalsupport for the ejector jet 3 and for urging it to null position, torquetube 15 also serving the additional function of acting as a conduit forhigh pressure fluid for the ejector jet 3. The jet 3 has a longitudinalaxial passage 30 which connects with one end of the tube 15, the otherend of tube 15 being fixed, as indicated at 31, in the cap 21 connectingwith a passageway 32 which terminates at the inlet marked P P 3 whichconnects with the inlet pressure P, as shown in the schematic FIGURES 6and 7. The passage 32 is formed partly in the base 22 and partly in thecap 21, as shown in FIG. 4. Passage 32 is provided with a suitableorifice 33 which reduces the pressure to a suitable value for the jet 3.

As described in my former patent, and as well known, the windings 27 ofthe torque motor 2 are connected in asuitable manner to an electricalsignal producing system which supplies an electrical control signal forswinging the armature 12 about the axis of the torque tubes 14 and 15.The direction of rotation of armature 12 and consequently of the jet 3is in accord with the direction of the electrical signal input to thewindings 27. The length of the are through which the armature 12 isrotated will be directly proportional to the magnitude of the electricalcontrol signal supplied to the windings 27. The torque tubes 14 andprovide a mechanical spring force which resists rotation of the armature12. When the electrical control signal is cut ofi, the torque tubes 14and 15 act to return the armature 12 and the ejector jet 3 to nullposition.

As shown in FIG. 2, the receptor jets 4 and 5 are longitudinally spacedin the direction of the longitudinal axis of the power spool 8. The jets4 and 5 are arranged at one end of a cylindrical rotary member 34 whichrotates on an axis parallel to the axis of the torque tubes 14 and 15,being, rotatably carried in a bearing bore 35 in an extension 36 of thecap 21. Extension 36 acts as a support and wall between the returnchambers 26 and 52.

As shown in FIGS. 2, 4, 6 and 7, receptor jet 4 connects with alongitudinal and radial passage 28 in the rotary member 34, this passageopening to an annular passage 37 in the periphery of rotary member 34,passage 37 connecting with passage 38 in the extension 36, that passageconnecting with passage 39 in the base 22, passage 39 leading to thepassage 40 at the end of sleeve 41 in which the power spool 8reciprocates. The passage 40 connects with a passage 42 at the end of ahollow spacer 43 having a port 44 in its end cap, this port opening intothe space 45 at the left end of the power spool 8. Ports 44 and 50 havea stabilizing action, as well known.

The other jet 5 similarly leads to the opposite end of the power spool,or valve spool 8, via the following: passage 29 in the jet spool 34,annular passage 46 in the periphery of rotary member 34, passage 47 insecond stage body 22, and passages 48, 49 and 50 leading to the rightend of the power spool 8, similar to the passages 40, 42 and port 44,previously described. The lower end of the extension 36 fits on theupper surface of the bottom wall 51 of a cavity in the base 22, aportion of this cavity consisting of the pressure chamber 26, aspreviously described, another portion of this cavity consisting of achamber 52 into which one end of the rotary member 34 projects, as shownin FIG. 4. This projecting end of 34 has a depending mechanical feedbackarm 53 which terminates in a ball 54 which frictionally has a bearingfit between the annular shoulders 55 and 56, as shown in FIG. 2. Theseshoulders are provided by spaced collars arranged at the middle portionof the power spool 8. The feedback control of the receptor jets 4 and 5is thus obtained through the coupling by the shoulders 55,

56 and the ball 54 on the arm 53 of the rotary member 34. Movement ofthe power spool in one direction, or the other, due to an electricalinput which changes the position of the ejector jet 3 results infavoring the pressure at one end or the other of the power spool, theresultant movement of the power spool being accompanied by acorresponding movement of the receptor jets 4 and 5. The power spool 8thus receives maximum pressure at its opposite ends for the nullposition and for all displaced positions of the receptor jets 4 and 5.

The annular grooves or channels 37 and 46 are housed in the bearing bore35 in the wall 36. The fluid pressure is hydraulically balanced in eachof the annular peripheral grooves or channels 37 and 46 in jet spool 34for the reason that fluid pressure existing at any point in theperiphery of such groove or channel is balanced by an equal and oppositepressure at a diametrically opposite position on the spool. Thus, theposition of the jet spool 34 is not influenced in any way by the fluidpressure from the receptor jets to the power spool.

The opposite ends of the base 22 are closed by caps 57 and 58 held inposition by suitable bolts, as indicated at 59 and 6t 7 As shown inFIGS. 6 and 7, the jets 4 and 5 remain centered with the jet 3 in allactuated positions of the ejector jet 3.

FIGS. 6 and 7 illustrate a well known arrangement wherein the powerspool 8 receives pressure from the inlet P, acting to control pressureto or from cylinders having passages indicated at C and C and exhaust orreturn, indicated at R.

As previously noted, the mass at opposite sides of the pivot provided bythe axis of the torque tubes 14 and 15, namely the mass of the armature,as compared to the jet 3, may be substantially equal, thus providingmass balance.

Also, as previously noted, the radial length of the ball 54 from theaxis of rotary member 34 is large compared to the radial length of thereceptor jets 4 and 5 from that axis which is conducive to highefficiency, as previously explained.

From FIGS. 6 and 7 it is apparent that movement of jet 3 in onedirection causes power spool 8 to move in the opposite direction, thelatter acting on the pivoted feedback arm 53 to move the jets 4 and 5 inthe opposite direction to that of the power spool 8, namely in the samedirection as jet 3.

I claim:

1. An electro-hydraulic servo valve including the combination of a pilotvalve and a power spool, the pilot valve having a polarized relay havinga winding and a swinger with an extension having an ejector jet, thepower spool controlling cylinder and exhaust ports, the power spoolhaving opposed pressure chambers supplied with fluid under pressure fromreceptor jets associated with the ejector jet, the improvement whereinsaid receptor jets are supported by a cylindrical member rotary about alongitudinal axis, wall means providing a bearing support for saidcylindrical member, a casing having a cavity, said wall means dividingsaid cavity into two chambers, one end of said cylindrical member withsaid receptor jets extending into one of said chambers, the

other end of said cylindrical member extending into the other chamber,where a feedback arm on said cylindrical member is provided for saidpower spool, and said feedback arm being controlled by said power spoolfor causing said receptor jets to follow said ejector jet.

2..An electro-hydraulic servo valve comprising an electricallycontrolled ejector jet, a receptor jet device having receptor jets forsaid ejector jet, a power spool having opposed pressure chamberssupplied with high pressure fluid from said receptor jets, said receptorjet device being in the form of a rotary cylindrical member, a wallhaving a bearing support for said rotary member, a casing member havinga cavity, said wall dividing said cavity into two chambers, said rotarymember having one end in one chamber with a feedback connection to saidpower spool, said one chamber being connected to a return chamber ofsaid power spool, said receptor jets being on the other end of saidrotary member in the other chamber, said rotary member having a pair ofannular peripheral channels housed in said wall, each of said channelsbeing in a fluid pressure path from one of said receptor jets to thecorresponding pressure chamber of said power spool, whereby said spoolis hydraulically balanced for fluid pressure in said path.

3. An electro-hydraulic servo valve according to claim 2, said casingmember which has said cavity being a second stage body housing saidpower spool, said wall being an extension on a first stage body for saidsecond stage body, said wall having an inner end abutting a bottom Wallof said cavity, said first stage body having a pivotal support for saidejector jet.

4. An electro-hydraulic servo Valve comprising an electricallycontrolled ejector jet, a receptor jet device having receptor jets forsaid ejected jet, a power spool having opposed pressure chamberssupplied with high pressure fluid from said receptor jets, said receptorjet device being in the form of a rotary cylindrical member, a wallhaving a bearing support for said rotary member, a casing member havinga cavity, said wall dividing said cavity into two chambers, saidcylindrical member having one end in one chamber with a feedbackconnection to said power spool, said one chamber being connected to areturn chamber of said power spool, said receptor jets being on theother end of said cylindrical member in the other chamber, saidcylindrical member having a pair of annular peripheral channels housedin said wall, a fluid passage in said cylindrical member from each ofsaid receptor jets to one of said channels, a fluid passage in said wallconnecting one of said channels with a fluid passage in said casingmember and the pressure chamber at one end of said power spool, andanother fluid passage in said Wall connecting the other channel with afluid passage in said casing member and the pressure chamber at theother end of said power spool, whereby said jet spool is hydraulicallybalanced for fluid pressure from said receptor jets to said power spool.

5. An electro-hydraulic servo valve comprising an ejector jet, a torquemotor controlling said ejector jet, a receptor jet device havingreceptor jets for said ejector jet, a power spool having opposedpressure chambers supplied with high pressure fluid from said receptorjets, said receptor jet device being in the form of a rotary cylindricalmember, a wall having a bearing support for said cylindrical member, acasing member having a chamher at each side of said wall, saidcylindrical member having one end in one chamber with a feedback linkcon nected to said power spool, said jets being on one side of saidcylindrical member and said feedback link being on the other side ofsaid cylindrical member, said one chamber being connected to a returnchamber for said power spool, said receptor jets being on the other endof said cylindrical member in the other chamber.

6. An electro-hydraulic servo valve including the combination of a pilotvalve and a power spool, the pilot valve having a polarized relay havinga winding and a swinger with an armature having an ejector jet, thepower spool controlling cylinder and exhaust ports, the power spoolhaving opposed pressure chambers supplied with fluid under pressure fromreceptor jets associated with the ejector jets, the improvement whereinsaid armature has a lateral extension for said ejector jet, saidarmature and said ejector jet being laterally oflset from each other andextending in opposite directions from said lateral extension, and torquetube means are provided for pivotally supporting said swinger on an axisextending transversely of the longitudinal axis of said swinger, saidtransverse axis being located at a position providing balance of themasses of said swinger at opposite sides of said transverse axis, arotary cylindrical member having a longitudinal axis substantiallyparallel to the axis of said lateral extension, said rotary memberhaving receptor jets for said ejector jet on one end thereof and havinga feedback arm on the other end thereof for said power spool, said powerspool having a cylinder centrally located with respect to the axis ofsaid winding, said feedback arm swinging in a plane passing through theaxis of said winding.

References Cited UNITED STATES PATENTS 2,724,397 11/ 1955 Ziebolz 137832,742,022 4/1956 Jacques 13783 3,017,864 1/1962 Atchley 91-3 3,137,3096/1964 Blase 13783 3,205,782 9/1965 Tourtellotte 91-3 3,211,182 10/1965Gyurik 137-625.61 3,233,623 2/1966 Gray 137625.62 X

ALAN COHAN, Primary Examiner.

1. AN ELECTRO-HYDRAULIC SERVO VALVE INCLUDING THE COMBINATION OF A PILOTVALVE AND A POWER SPOOL, THE PILOT VALVE HAVING A POLARIZED RELAY HAVINGA WINDING AND A SWINGER WITH AN EXTENSION HAVING AN EJECTOR JET, THEPOWER SPOOL CONTROLLING CYLINDER AND EXHAUST PORTS, THE POWER SPOOLHAVING OPPOSED PRESSURE CHAMBERS SUPPLIED WITH FLUID UNDER PRESSURE FROMRECEPTOR JETS ASSOCIATED WITH THE EJECTOR JET, THE IMPROVEMENT WHEREINSAID RECEPTOR JETS ARE SUPPORTED BY A CYLINDRICAL MEMBER ROTARY ABOUT ALONGITUDINAL AXIS, WALL MEANS PROVIDING A BEARING SUPPORT FOR SAIDCYLINDRICAL MEMBER, A CASING HAVING A CAVITY, SAID WALL MEANS DIVIDINGSAID CAVITY INTO TWO CHAMBERS, ONE END OF SAID CYLINDRICAL MEMBER WITHSAID RECEPTOR JETS EXTENDING INTO ONE OF SAID CHAMBERS, THE OTHER END OFSAID CYLINDRICAL MEMBER EXTENDING INTO THE OTHER CHAMBER, WHERE AFEEDBACK ARM ON SAID CYLINDRICAL MEMBER IS PROVIDED FOR SAID POWERSPOOL, AND SAID FEEDBACK ARM BEING CONTROLLED BY SAID POWER SPOOL FORCAUSING SAID RECEPTOR JETS TO FOLLOW SAID EJECTOR JET.